Patent Application
20200103172
The invention relates to a device for the transfer of heat in particular for application in a motor vehicle. The heat is herein preferably transferred between a coolant as a first fluid, for example water or a mixture of water and glycol, and air as a second fluid. The device comprises an assembly of tube elements for the conduction of the first fluid as well as at least one tube plate with passage apertures for passing the tube elements through the tube plate.
The invention relates, moreover, to a system and a method for the manufacture of a device for heat transfer.
Coolant-air heat exchangers known in prior art for transferring heat from a coolant of a coolant circuit to ambient air are applied in so-called high-temperature coolant circuits for discharging the heat of an internal combustion engine. The coolant-air heat exchangers constructed of aluminum comprise a number of tubes secured in tube plates, as well as fins and side elements and coolant collectors disposed across crimping joints. These diverse elements must be assembled into heat exchangers. The tubes oriented in parallel and arranged in a matrix serve for the conduction of liquid coolant between the collectors. The coolant collectors disposed on both sides at the ends of the tubes are conventionally sealed against the tubes or tube plates by means of ethylene propylene diene monomer sealing elements, abbreviated as EPDM seals. The tubes, tube plates, fins and side elements are either fabricated as so-called plug coolers employing a plug method, or are fully soldered as so-called solder coolers.
When using the soldering method in a controlled atmosphere, abbreviated as CAB or Controlled Atmospheric Brazing, a matrix of tubes and fins is interconnected and also connected to tube plates, if appropriate, as a metallic element of a collector. In the plug method the welding or soldering of adjacent structural metal parts is avoided by using a mechanical assembly procedure or MA of the matrix and the collector.
The air absorbing the heat from the coolant flows along the outside of the tubes and thus between the tubes. The fins or ribs disposed on the outside between the tubes serve to enlarge the air-side heat transfer area and thus to raise the heat transfer capacity.
The known coolant-air heat exchangers have inadequate continuous service capability against rapidly changing temperatures of the coolant. In extreme application cases the coolant-air heat exchanger may be rapidly cooled to temperatures in the range of −20° C. to −10° C. and, due to rapidly opening valves in the coolant circuit, may be charged with coolant at a temperature of 120° C. The coolant-air heat exchangers are herein subjected to extreme temperature alternations and experience thermal shock. Due to time-delayed thermal expansions of the individual tubes, extremely high material stresses occur.
While, due to their friction-bearing connections as elements of the collectors between the tubes and the tube plates, plug coolers have high resistance capabilities against temperature changes of the coolant; however, due to their friction-locked connections between the tubes and the fins, they also have lower cooling capacities than soldered coolers. Soldered coolers, on the other hand, due to rigid solder connections between the tubes and the tube plate, have limited durability under temperature changes and the thermal expansions of individual tubes entailed therein.
DE 10 2015 113 905 A1 discloses a heat exchanger and a method for the fabrication and assembly of a heat exchanger, in particular of an air flow heat exchanger with a mechanically mounted collector for application in motor vehicles. The heat exchanger comprises a fully metal-bonded matrix of a multiplicity of parallel metal tubes and a multiplicity of metal ribs. The tubes comprise a heat transfer section with an oblong cross section form, in each instance with two opposing longer sides and two shorter sides. At least one tube is connected on a first end section with a first collector by means of at least one flexible element which extends about the first end section of the tube, in order to provide the sealing and to enable relative movement between the mechanically joined tube and the first collector due to the thermal expansion and contraction of the matrix.
Herein, by using a method in which the tubes and fins are soldered without tube plates and the tube plates are subsequently plugged onto the tube under press fit and sealed in sealings, a synergy of the fabrication methods of a plug cooler and a solder cooler are described. As a consequence of the degraded material properties due to the exposure to temperatures of more than 600° C. during the soldering process in the solder furnace, the tubes, in particular in the region of the ends, cannot permanently withstand the counterforces applied through the sealing by press fit with the demand to ensure the sealing fit over the entire circumference of the tube.
The heat exchangers and methods of their production known in prior art are limited to the use of tubes, in particular of welded tubes, with a tube breadth of approximately 10 mm to 11 mm in order to withstand the sealing pressure. Heat exchangers or matrices with greater breadth are, for example, constructed of several tube layers or tube planes.
Conventional aluminum tubes of heat exchangers applied in motor vehicles are either welded or folded and hard soldered. However, welded tubes can only be fabricated up to a maximal breadth in the range of 14 mm to 20 mm since the tubes with greater broadness tend to bulge up and collapse especially during high pressure-pulse loading.
Demands and development trends now lead to the implementation of welded tubes with greater breadth, for example with a breadth up to 40 mm, to meet higher demands made of the cycle stability and cleanness of the flow channels formed in the tubes which, for example, can be impaired through residues of fluxing agents, as well as escalating requirements made of the heat transfer. For adequate durability, flat tubes of aluminum for applications with internal pressures up to 4 bar have to be built with a central internal structure element.
For heat exchangers with only one tube plane, extruded, flanged or welded B-tubes are under consideration. The application of B-tubes, termed so due to the flow cross section in the form of a B, for the heat exchanger with press fit between tube and coolant collector has failed in the past due to leakage between the seal and the tubes at the seam of the B-tube.
The invention addresses the problem of providing a device for the efficient heat transfer between two fluids, in particular between a liquid fluid as the coolant and air, as well as a method for the manufacture and assembly of the device. The heat exchanger is to have maximal impermeability even under large temperature alternations, which means the heat exchanger is to have high thermal shock resistance. The heat exchanger is to be capable of transferring maximal heat capacity at minimal constructed size or minimal installation space requirement. Moreover, the heat exchanger is to be of minimal weight as well as cause minimal production and material costs.
The problem is resolved through the subject matters with the characteristics of the independent patent claims. Further developments are specified in the dependent patent claims.
The problem is resolved through a device according to the invention for the heat transfer between a first fluid and a second fluid. The device comprises an assembly of tube elements for conducting the first fluid through them, with at least one tube plate with passage apertures as well as at least one sealing element with passage apertures. The tube elements are in each instance developed with a first, nondeformed region and at least a second, deformed region disposed at one end of the tube element.
According to the concept of the invention, the tube elements are each guided through the passage apertures. The sealing element is herein in each instance disposed between an outer surface of the second region of a tube element and an edge of a rim of the passage aperture of the tube plate. With the interspaced sealing element the connection of the at least one tube plate with the passage apertures is impermeable to fluids. The form of each of the passage apertures of the tube plate and of the sealing element correspond to one another as well as to an outer form of the tube elements. Herein one tube element is advantageously passed through a passage aperture such that to each end of a tube element in each instance precisely one passage aperture is assigned.
The tube elements are in each instance developed as flat tubes of a metal with flow channels for conducting through them the first fluid, in particular a coolant. The flow channels are herein separated from one another by at least one internal structure element. In the second region the cross section of the tube elements is flared in a plane oriented perpendicularly to a longitudinal direction.
The tube elements consequently comprise with the first, nondeformed region a region of heat transfer in which there is flow of the second fluid, in particular air, circulating about the tube element, and with the second, deformed region advantageously a region of a connection with the tube plate.
According to a first alternative embodiment of the invention, the tube element has a B-shaped cross section. The internal structure element is herein implemented of two shanks, formed into a web, with a connection region as a central structure element.
The connection region preferably includes a gap which extends along the longitudinal direction from a first end to a second end on an upper side of the tube element and is at least partially closed by means of a welding seam. The welding seam can extend continuously from the first end to the second end of the tube element or be developed exclusively in the at least one second region of the tube element.
According to a second alternative embodiment of the invention, the tube element is developed as a multi-channel flat tube with a multiplicity of internal structure elements which, developed as a web, in each instance separate two adjacently placed flow channels for the conduction of the first fluid. The cross section of the tube element is preferably developed with the flaring exclusively in regions of the flow channels.
According to a further development of the invention, the tube element has in a region of maximal flaring a height in the range of 3.0 mm to 5.6 mm and in the connection region a height in the range of 1.5 mm to 2.1 mm. The total breadth of the tube element is advantageously in the range of 20 mm to 55 mm, in particular in the range of 20 mm to 26 mm.
According to a third alternative embodiment of the invention, the tube element comprises at least one groove extending in the longitudinal direction on an upper side as well as on a lower side or notch points disposed on an upper side as well as on a lower side, each with a connection region. The internal structure element is herein developed by at least one weld joint in the connection region. The weld joint of the tube element is advantageously either continuous or developed as a fluted spot weld pattern.
The connection region preferably terminates at a predetermined distance from at least one end of the tube element such that the second region has a planar upper side as well as a planar lower side.
A further advantageous embodiment of the invention comprises that the tube plate is developed as a side wall element of a collector of the device for heat transfer.
The device for heat transfer can preferably be developed with two tube plates with passage apertures as well as with two sealing elements with passage apertures. The tube plates are in each instance connected fluidically impermeably with the tube elements, wherein the passage apertures in each instance correspond in their form with an outer form of the tube elements and each tube element is disposed with a first end having been guided through a passage aperture developed in a first tube plate and with a second end having been guided through a passage aperture developed in a second tube plate.
The tube elements are preferably developed in a straight line and advantageously of an aluminum alloy.
According to a further development of the invention, the tube elements are aligned in one row or in several rows within the assembly.
The tube elements of a row are preferably disposed next to one another and in parallel as well as with their broad sides toward one another such that between directly adjacent tube elements in each instance one flow path for the second fluid, in particular the air, is developed. In the flow paths of adjacently disposed tube elements advantageously fins or ribs are disposed for changing the flow cross section and/or for enlarging the area for heat transfer. The fins or ribs are preferably developed of an aluminum alloy.
The advantageous embodiment of the invention enables the use of a device according to the invention for heat transfer as a coolant-air heat exchanger in a coolant circuit, in particular in an engine coolant circuit of a motor vehicle.
The problem is also resolved through a system according to the invention for the manufacture of a device for heat transfer between a first fluid and a second fluid with the above characteristics. The system comprises solder tools for joining an assembly of tube elements with interspaced fins as well as means for flaring ends of the tube elements for connecting the tube elements with a tube plate. The solder tools are developed with a retaining frame with at least one tube-fixing element for retaining the tube elements at an end face as well as plug-in elements disposed on the tube-fixing element. The tube elements can herein be plugged with the open cross sections of the end faces onto the plug-in elements. The means for flaring the ends of the tube elements are developed from a stamping element with guide elements and flaring elements or with pin elements for penetration with a first end into the open cross sections of the end faces of the tube elements. The guide elements in connection with the flaring elements or the pin elements are herein spaced apart oriented correspondingly with the disposition of the tube elements. The pin elements are fixed through base elements and coupled with one another at second ends, distal to the first ends, across a connection element. The guide elements are connected with the flaring elements and the flaring elements with the stamping elements.
According to a further development of the invention, the tube-fixing elements are disposed on the retaining frame such that they are movable in the longitudinal direction of the tube elements. The tube-fixing elements are advantageously fixed on the retaining frame across threaded connections, which are developed in particular as rivets or bolts or screws, developed with an elongated hole.
A further preferred embodiment of the invention comprises that the pin elements are connected with the connection element across securement elements, such as rivets or bolts or screws.
The problem is furthermore resolved through a method according to the invention for the manufacture of a device for heat transfer between a first fluid and a second fluid, with the above characteristics. The method comprises the following steps:
In summary, the device according to the invention for heat transfer and its manufacture comprise diverse advantages:
Further details, characteristics and advantages of embodiments of the invention will become evident based on the following description of embodiment examples with reference to the associated drawing. Therein depict:
Depending on the power requirement, the assembly 2 built of the flat tubes 3 is implemented as a single row or multi-row assembly and is scalable in size, which means in particular in length or in width. The tube elements 3 shown in
The tube elements 3 aligned next to and parallel to one another, are disposed within one row with their broad sides toward one another such that between directly adjacent tube elements 3 in each instance one flow path for a fluid, in particular air, is formed. The flow path extends herein in each instance between the tube elements 3. The tube elements 3 of one row are dispoflushsed with one another and extend in each instance between two collectors 9. The internal volumes of the tube elements 3 are connected with the internal volumes of the collectors 9.
In the flow paths, and thus in interspaces of adjacently disposed tube elements 3, elements are disposed for changing the flow cross section and/or for enlarging the area for heat transfer. Fins 4 are developed as elements for changing the flow cross section and/or for enlarging the area for heat transfer. Alternatively, ribs could also be applied. Like the tube elements 3, the fins 4 are preferably implemented of a material that is a very good heat conductor, such as an aluminum alloy.
In the assembled state at the end faces or at the narrow sides of the assembly 2 tube plates 5 are provided that in each instance can also serve as a side wall element of a collector 9. As end faces are herein denoted the sides toward which the ends of the tube elements 3 are oriented. The tube plates 5 are each developed in the form of a substantially rectangular metal sheet, in particular of an aluminum alloy, as a deep drawn part, stamped part or hydroformed part. As the metal sheet is herein understood a flat rolling mill finished product of metal. By hydroforming, also termed high-pressure metal forming, is understood the forming of the sheet in a closed forming mold by means of pressure, which is generated for example through a water-oil emulsion in the mold.
The tube plates 5, rounded off in the proximity of the corner, as well as also the sealing elements 7 comprise passage apertures 6, 8 for receiving the tube elements 3. The passage apertures 6 of the tube plates and the passage apertures 8 of the sealing elements correspond to one another and to the outer dimensions of the tube elements 3 in order to establish a fluidically impermeable connection between the individual tube elements 3 and the tube plates 5.
The tube plates 5 disposed on the sides facing each other of the collectors 9 are fixedly connected with the tube elements 3. Due to the sealing element 7, the fixed connection is in each instance to be viewed as technically impermeable, zero-leakage connection. The tube plates 5 are disposed on the assembly 2 at the narrow sides of the tube elements 3 oriented perpendicularly to the tube elements 3.
The flow cross section of the tube element 3a is oriented in a plane spanned by a direction of breadth y and a direction of height z. The tube element 3a according to
The connection region 14a of the first shank 12 with the second shank 13 on the upper side 10a of the tube element 3a developed with the B-shaped cross section comprises a small gap substantially circular in shape with a diameter of approximately 0.18 mm. Using exclusively compressed sealing elements 7, the gap extending over the entire length of the tube element 3a is extremely difficult to seal against the tube plate 5. In the proximity of the gap sufficient compression of the sealing element 7 cannot be ensured and the probability of leaks is consequently high.
To seal the tube element 3a against the tube plate 5, the upper side 10a of the tube element 3a, at least in the proximity of the connection with the tube plate 5, is planar. After the forming of the tube element 3a by milling and folding by means of a tube fabrication machine, the connection region 14a is worked by means of welding, in particular laser welding. In this process the gap is closed. For the subsequent soldering of the assembly 2 in a CAB process, the material of the face layer or of the coating layer and the base material or the core material are mixed with one another on the welded surface along the connection region 14a. The surface of the weld seam is resistant to the CAB process and does not dissolve during the CAB process.
The laser welding can be carried out on site only in the region of the ends of the tube elements 3a, and thus in regions of the contact on the tube plate 5, at which the tube element 3a is sealed with the sealing element 7 against the tube plate 5 or is soldered to the tube plate 5. It can also be carried out continuously along the entire length of the tube.
The tube element 3a welded in this manner has, in particular in the proximity of the weld seam, a surface with smooth transition radii and is developed as planarly as possible. In
Shanks 12, 13 in the middle of the B-shaped cross section of the tube elements 3a serve in each instance as a rib, or as a web, to facilitate the sealing pressure that has to be applied for the sealing against the tube plate 5. The B-seam rib support enables the use of tube elements with a maximal total breadth in the range of 20 mm to 25 mm and therewith greater widths than is the case in known flat tubes of prior art.
The at least partially flared tube element 3a has now, for example at a total breadth of approximately 24.3 mm, in the region of maximal flaring a height of approximately 3.7 mm.
The deformed wall of tube element 3a at the tube ends is developed continuously and without fractures. The form of deformation increases, for one, the structural tube wall thickness and strength and, for another, serves for reinforcement and sealing within the passage apertures 6 in the tube plates 5.
The tube element 3a in a state of final flaring has now, for example at a total breadth of approximately 24.4 mm, in the region of maximal flaring a height of approximately 5.6 mm. The height in the nearly unchanged connection region 14a is approximately 1.5 mm.
Flaring of the tube wall or of the flow cross sections of the flow channels or chambers at the tube ends, in particular in the direction of height z, is exclusively possible in the regions between the webs 17.
In
The stamping element 18b developed with guide elements 20b and flaring elements 21b is disposed during the process of flaring the tube wall or of the flow cross sections of the flow channels at the end faces of tube element 3b such that the guide elements 20b and flaring elements 21b, oriented in each instance in a common direction, are oriented in the longitudinal direction x of tube element 3b. To each flow channel is herein assigned a guide element 20b with a flaring element 21b.
When moving the stamping element 18b in the direction of motion 19, which extends in the longitudinal direction x according to
The tube element 3b is now developed with a first, nondeformed region 15b as the region of heat transfer in which a fluid flows about the tube element 3b and a second, deformed region 16b as a region of deformation as well as connection with the tube plate 5.
In the end state of having been flared the tube element 3b now has in the region of maximal flaring a height of approximately 3.0 mm for example. The height in the nearly unchanged connection region is approximately 2.1 mm.
In particular due to the development of the internal rib structures, the tube elements 3a, 3b enable the single-row assembly 2 of a device 1 with a deeper heat transfer core, which can conventionally only be achieved with a multi-row heat transfer core. With a single-row assembly 2 of tube elements 3a, 3b, the devices 1 can herein have a breadth of more than 11 mm.
The device 1 developed with the tube elements 3a, 3b has furthermore a very high thermal shock resistance due to the flexible, non-rigid connection of tube element-sealing element-tube plate, which is developed on at least one side of the assembly 2.
In
The internal structures required to meet the high internal pressure pulse requirements are each enabled by a welding connection within the tube elements 3c, 3d developed in the connection regions 14c, 14d. The central structure elements in particular for the vertical rigidity in the direction of height z of the tube element 3c, 3d under internal pressure, are each depicted by a groove or notch points having a welded connection on the surface of the tube elements 3c, 3d. The groove can herein be developed within a first region 15c, 15d as a region of heat transfer according to
The grooves terminate at a predetermined distance from the tube ends in order to provide in a second region 16c, 16d of the tube ends, as a region of deformation, a planar upper side 10c, 10d as well as a planar lower side 11c, 11d for the connection of the tube elements 3c, 3d, guided through the passage apertures 6 in the tube plates 5, with the tube plates 5. The internal welded connection of the tube element 3c, 3d extends between the regions of the tube ends in order to enable a mechanical mounting of the tube element 3c, 3d on the tube plate 5.
The tube elements can furthermore be developed with a multiplicity of grooves, which means with a number greater than one, and/or with a fluted spot weld pattern.
The tube elements 3c, 3d, developed as welded flat tubes, can be developed with a greater dimension in the direction of breadth y than conventional tube elements and this also in order to satisfy higher demands made of the heat transfer. The internal cleanness is, moreover, greater than in flat tubes with a B-shaped cross section, that means compared to folded and soldered tube elements since no fluxing agent is required in the welding process.
In motor vehicle heat exchangers of prior art with a dimension in the direction of breadth y of at least 20 mm most frequently flat hard-soldered aluminum tubes are utilized. Inner soldering of folded tube elements, however, requires an internal flux. Residues of the fluxing agent are, in turn, a main source of contamination of the coolant circuit. For example, when applied in fuel cell systems, a welded tube element is exclusively used which has passed through a special cleaning process.
In
In
Due to the flaring of the tube elements 3b, the tube elements 3b are fixedly and fluidically impermeably connected with the tube plate 5b with the sealing elements 7b disposed between the tube elements 3b and the margins of the passage apertures 6b of the tube plate 5b.
The assemblies 2 furthermore comprise fins 4 developed between the tube elements 3a, 3b.
In
Tube elements 3 with the interspaced fins are fixed within the retaining frame 22 such that the assembly in its entirety can be soldered together, for example in a solder furnace, and the individual components can be interconnected. The tube elements 3 having the same length in each instance are disposed in a single row and flush at the end faces.
The tube elements 3 are retained at the end faces by means of a tube-fixing element 23. The tube elements 3 are herein placed with the open cross sections onto plug-in elements 24 developed on the tube-fixing element 23. This is done to avoid movements of the tube elements 3 particularly transversely to the longitudinal direction. The tube-fixing elements 23 are disposed on the retaining frame 22 movably in the longitudinal direction for the purpose of compensating changes of length due to thermal expansion. The tube-fixing elements 23 are for example fixed across bolt connection with an elongated hole on the retaining frame 22.
Following the process of soldering, the assembly of tube elements 3 and fins 4 can be removed from the retaining frame 22 as a soldered core of a device for heat transfer without tube plate or collectors.
In
In
It is especially clear in the exploded representation according to
In
After welding the tube elements 3a, developed as flat tubes with a B-shaped cross section, or after soldering the tube elements 3c, 3d, developed with grooves, or after soldering the tube elements 3, listed here to encompass collectively the tube elements 3a, 3c, 3d and the tube elements 3b developed as extruded multi-channel flat tubes, assemblies of tube elements 3 with fins are obtained as a joined unit. The heat transfer core is mounted by soldering. The tube elements 3 are not deformed at the ends.
At the start of flaring the ends of the tube elements 3, the sealing element 7 and the tube plate 5, also according to
According to
Every pin element 25 is developed with a limit stop 29 which delimits the flaring element 21 and marks the end of the insertion of the pin elements 25 in the direction of motion 19 into the tube element 3. The limit stop 29 developed as a step herein abuts on the end face of the now flared and deformed tube element 3, which is especially clearly shown in
The method for flaring the ends of the tube elements 3, and therewith the production of a flexible and fluidically impermeable connection between the tube elements 3 and the tube plate 5, is completed by removing the pin elements 25 from the tube elements 3 according to
The method for connecting the tube elements 3 with the tube plate 5 ensures that the tube elements 3 are disposed in precise positions of the passage apertures 6, 8 and in this manner a certain and secure fluidically impermeable connection is obtained. To ensure sufficient, certain and reliable compression of the sealing element 7, a specific magnitude of flaring is preset as an end expansion of the tube elements 3. The compression of the sealing element 7 is therein in the range of 10% to 50% compression, wherein the major portion of compression is attained directly after mounting the tube plate 5 with the sealing element 7 on the tube elements 3, the tube elements 3 are, for example, flared in the direction of height z by up to +0.2 mm as well as in the direction of breadth y, and thus in broadness, by up to +0.1 mm.
With the flaring of the ends of tube elements 3 a further structural augmentation of the tube wall is provided. Herein the tube wall is shaped continuously without experiencing fractures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 113 849.8 | Jun 2017 | DE | national |
| 10 2018 111 585.7 | May 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2018/006129 | 5/30/2018 | WO | 00 |
